Frank Stella decides he wants to be interviewed behind the huge desk of his London dealer. "I'm head of the corporation," he jokes. He's wearing a fleece with Team Stella emblazoned on it. A few minutes later a former director of the Tate Gallery pops in to say hello. Whatever Stella does now, even if he goes senile and starts exhibiting doodles, he will be remembered as a great American artist. He has known this since he was in his early 20s.

Stella was born in 1936, grew up in a suburb of Boston, and was just out of Princeton when he produced his so-called Black Paintings. With such grimly evocative titles as Die Fahne Hoch! (The Banner High), named after a Nazi marching song, and The Marriage of Reason and Squalor, Stella's first paintings are shocking. Each consists of a layering of black rectangular stripes, fanning out like the citadels of some lost Assyrian city, taking their shape from the canvas itself. They have been interpreted as both an attack on the high modernist art of the abstract expressionist artists who came before him - Pollock, Rothko and Newman - and the continuation of their achievement. He has been acclaimed as both the founder of minimalism and the last artist to stand against it.

Either way, Stella's debut was a sensation. His Black Paintings were shown at the Museum of Modern Art in New York in 1960 in an exhibition that also showcased Jasper Johns and Robert Rauschenberg. But the 24-year old Stella stood out. The paintings were bought by the museum, and are now displayed alongside such masterpieces as Johns's Flag, Pollock's One and Matisse's Piano Lesson.

Stella was a prodigy, a figure of exceptional glamour, the champ, characterised as a genius while still at Princeton. Genius is a big word, but before he left university, Stella was accustomed to people applying it to him and the praise in the 1960s only got more elevated.

But what does a genius do next?

Frank Stella is in London to promote a book, Frank Stella's Moby Dick by Robert K Wallace. It chronicles and analyses the series that Stella himself sees as central to his later career - artworks made during the 1980s and 1990s, including lithographs, sculptures and installations, each of which takes its title from one of the 135 chapters of Herman Melville's great American novel. "Why couldn't there be a British Melville?" wonders Stella. "They had great explorers, but, I don't know, a quest for God or chasing the white whale is different from a quest for empire, right? The British want to really own it somehow; the Americans just want to be able to grasp it. Maybe they're slightly less materialistic - it's hard to believe."

Indeed it is. But American art such as Stella's is less materialistic, pushing for abstraction while British art remains defiantly earthbound. Stella's spiritual apprehension of the visual world may be linked to his origins in puritan Boston (not that far from Nantucket from where the Pequod sets sail in Moby Dick).

It occurs to you, seeing him behind that big desk and listening to his dryly humorous voice telling his tale, that Stella himself would make a character in a great American novel. He's a modern Queequeg - the supremely talented harpoonist in Moby Dick, who, when asked for his credentials, throws his harpoon at a tiny blob of tar on a roof, hitting the target dead centre. If that was a whale's eye, he says, the whale would be dead now. Stella once told his friend Michael Fried, the critic and art historian, that his own idea of genius was the baseball player Ted Williams, because he could see the ball perfectly and then hit it right out of the park.

Stella became a revered American artist when he was in his early 20s, but he didn't rest on his laurels and he didn't make more and more brutal paintings. Instead he tried to stage that elusive second act. He began to make his paintings more complex in structure, colour and shape, and then brought them off the wall, welding, shaping, doing what a sculptor does, but still - in fact more recognisably than with the Black Paintings - seeing as a painter.

Critics have been, to say the least, divided about what happened to the art of Frank Stella. Right now, art is in a swing back to the minimalist objective art of the 1960s; artists are acclaimed for their starkness, and Stella's early work looks modern in a way that his later work does not. Young artists are transfixed and influenced by Die Fahne Hoch! or Six Mile Bottom (1960), with its silvery authority, in a way they are not by 138 attractive but inessential works responding to Moby Dick. But then, as Stella says, when he started out, some critic described his stripe paintings as "boring". "People say I jump around a lot, but it seems to me like I spend plenty of time on everything I work on. I can't say I left many stones unturned. But things do wear out for me."

If Stella's career were a great American novel, the most important supporting character would be Fried. It's not just that they went to Princeton together and both became towering figures in the nation's cultural establishment (Fried has become one of America's most lauded academics) but that Fried's and Stella's ideas are intertwined. At one point, Stella criticises the art of his contemporary, the minimalist Donald Judd, as "literalist". It's one of Fried's favourite words.

Fried loathed the minimalists - Donald Judd, Robert Morris, Carl Andre - artists who emerged in New York in the 1960s, wanting to do something different from the generation of Pollock and Rothko, and who simply presented "objects" to the viewer, brutally shorn of traditional aesthetic values. In a famous 1967 article in the New York magazine Artforum, Fried denounced minimalism as "theatrical" - claiming that it made cheap claims on people's attention - and "literal" - ie misunderstanding the nature of art as illusion. Modern art, he argued, was the opposite of this - a repudiation of theatre, false values, and the merely objective; ultimately, a spiritually uplifting art. It's a debate that still matters because minimalism is the underpinning of art today. All those vitrines and casts, the shark and the house.

But what did Fried have to say about his friend Stella? For many, Stella's early paintings were the founding statements of minimalism. Fried argued, however, that as Stella developed, he was making it more and more plain that he was a painterly painter, who believed in art, and that his works, with their increasing richness, were deliberate corrections of the minimalist mistake. Yet, in his youth, Stella said some tough and undeniably minimalist things about art. He said that in his paintings, "What you see is what you see". He said, "I tried to keep the paint as good as it was in the can."

Today he says that he never wanted to destroy anyone's idea of a well-made painting. The Black Paintings are, "quite painterly - although they're one colour, they seem to me to be closer to Rothko than just about anything else. The idea that these were such a rejection of abstract expressionism I don't think is accurate." Stella describes his Moby Dick series as a kind of tribute to those Captain Ahabs, the abstract expressionists. "They're still the generation I admire. This is paying my debt, or not so much paying my debt as expressing my admiration for the abstract expressionist generation that I grew up with and that I admired the most, and that I still admire."

Moby Dick, Ahab's doomed pursuit of the mystical image of the great white whale, was a touchstone for the abstract expressionist painters. Jackson Pollock named at least one painting after the novel and intended to give its name to his classic early work Pasiphae, then switched to something from Greek myth because his patron Peggy Guggenheim didn't like the Melville reference. Pollock's sense of space is absolutely suggested by Melville, and the rolling, wild wave forms of Stella's Moby Dick - inspired by observing beluga whales swimming in the New York aquarium - are very Pollock.

In the Moby Dick series, Stella sees himself challenging the deepest assumptions of modern art with a new understanding of what abstraction can do: "Abstraction in the 20th century is dependent on cubism, which is arranging planes in space, but the planes are arranged in a kind of stiff and geometric kind of way. Once the planes begin to bend and curve and deform then you get into what happens in Moby Dick - it's a way of opening things up for abstraction."

Stella certainly has more in common with the American painters of Pollock's generation than he does with the ironising, theatrical minimalists who thought he was on their side. But he has ended up cast adrift in an open boat, an American individualist making his own eccentric way, as the watchers from the shore try and fail to categorise him - a minimalist, a modernist, a postmodernist. This makes the novel in which he is a character, the champ, the American genius, a troubling read. Frank Stella has never done anything that lived up to his early work. But who has?

 Frank Stella's Moby Dick by Robert K Wallace is published by Michigan University Press, price £42.50.